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2 l JLC l FEBRUARY 2011

On Site With Zip System Sheathing

Get faster dry-in and a tighter building

envelope without housewrap

Last year, we tried Huber’s Zip System wall and roof sheathing on a

spec house to see how well these products would work with our con-

struction methods. Zip panels have the same structural qualities as

other types of OSB sheathing, but they also have a water-resis-

tant kraft overlay on their outside face. After they’re nailed

off, the seams are sealed with a specially

designed tape. Then the siding and roof-

ing can be applied directly to the panel

face, with no need for a separate water-

resistive barrier or roofing underlayment.

A big incentive for me at the time was

a $3-per-panel manufacturer’s rebate

that allowed us to test the Zip panels and

tape without having to raise the price of

the house we were building. That rebate

was only for first-time users and has since

expired, but we’re still using Zip System

sheathing. That’s because despite the pre-

mium we pay for the sheathing and tape,

we’ve found that — with a few exceptions

— the installed cost compares favorably

to that of conventional sheathing with

housewrap.

There are numerous benefits to using

Zip sheathing, including faster dry-in and

less wind damage to the weather barrier

before siding and roofing application. But

possibly the biggest advantage is that the

taped panels create a continuous air bar-

rier, making it easier to build a tight shell

by Tim Uhler

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FEBRUARY 2011 l JLC l 3

On Site Wi th Zip System Sheathing

and meet the 2009 International Energy

Conservation Code’s requirements for air

leakage. Under the newest version of the

energy code, air leakage needs to be less

than seven air changes per hour at a pres-

sure of 50 pascals (ACH50) as tested with

a blower door. (Washington State, where I

work, has recently adopted a similar code.)

If you’re committed to building energy-

efficient houses or you work in an area that

has adopted the IECC, using Zip sheathing

might simplify how you detail the build-

ing envelope.

Cutting and InstallationWe work in an earthquake zone and typi-

cally run our sheathing vertically to reduce

the need to block panel edges. So we appre-

ciate the fact that the long edges of the

wall panels have a self-spacing profile that

allows us to butt the panels tightly together

at this critical joint (see Figure 1, next page).

Along the shorter 4-foot panel edges, a stan-

dard 1⁄8-inch gap is still required.

Nailing. Zip sheathing feels a bit stiffer

and denser than standard OSB sheath-

ing. Even so, when we first nailed off the

Zip panels, it seemed that we were over-

driving an unusual number of fasteners.

According to Huber, overdriving doesn’t

compromise the panels’ water resistance

or void the warranty, but the company

recommends taping any fastener driven

more than 1⁄8 inch below the surface of the

substrate. When we slowed our pace a lit-

tle instead of blasting away with our nail

guns, we had better success setting the

nail heads flush. This simple step didn’t

cost us much extra time, and we didn’t

have to reset the depth-of-drive on our

guns or lower our compressor settings.

Even when the nail heads are perfectly

flush during installation, though, we’ve

noticed that when we come back later to

install siding, the nails all look slightly

overdriven. My guess is that the sheath-

ing absorbs a little of the moisture in the

air and swells, so on our next house we

plan to try using Bostitch HurriQuake

nails (800/556-6696, bostitch.com). These

nails have a 25 percent larger head and

a smaller .113-inch shaft diameter (as

opposed to the .131-inch-diameter fasten-

ers we’re using now), which I think will

Zip System sheathing combines

OSB structural panels with a

layer of resin-impregnated kraft

paper. The .01-inch-thick overlay is

permanently bonded to the outside

face of the panels in the press as the

OSB is manufactured. The panels are

manufactured for use as wall and roof

sheathing; the roof sheathing pan-

els have a gritty surface texture to

improve traction. Roof panels come

in 1⁄2-inch and 5⁄8-inch thicknesses in

a standard 4x8 size; wall panels come

in 7⁄16-inch and 1⁄2-inch thicknesses,

in sheet sizes from 4x8 to 4x12,

according to literature published at

the manufacturer’s websites (huber

wood.com, zipsystem.com). Wall panels are available

either square-edged or with a self-spacing machine-

edged profile; roof panels can be tongue-and-groove,

square-edged, or machine-edged.

Getting rid of housewrap? The ICC evaluation

report for Zip System wall sheathing states that it is

“used as combination wall sheathing, air barrier, and

water-resistive barrier” — no doubt a big reason for

its increasing popularity in some parts of the country.

While housewrap can be installed

quickly by anyone, it’s rarer to see

it installed well, and not uncommon

to see it torn and flapping in the

breeze — which would be impossi-

ble with a bonded WRB. Of course,

the “system” requires the application

of tape, which is time-consuming and

expensive. But for builders looking

for an airtight shell, the tape is just

another part of the attraction. And

though housewrap may be omitted,

some builders using Zip wall pan-

els include it anyway, because they

are reluctant to rely on taped joints

to permanently keep out water and

because they want the additional

water-resistant layer for weaving in cap flashings over

windows and doors (see “High-Performance Homes

on a Budget,” 01/11).

Huber claims a vapor permeance of 12 to 16 perms

for the overlay on the Zip wall panels. That means a wall

sheathed with Zip panels will have a vapor profile simi-

lar to that of a wall sheathed with conventional OSB and

covered with Typar, which has a permeance of around

12 (by comparison, Tyvek is 58 perms). — The Editors

About Zip System Sheathing

ZIP wall and roof panels consist of OSB structural sheathing with a water-resistant, resin-impreg-nated kraft facing.

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4 l JLC l FEBRUARY 2011

help keep the nail heads flush with the

face of the sheathing.

Cutting. The denser panel material

definitely takes a toll on blades and bits,

at least compared with standard OSB. We

noticed when we were cutting 1⁄2-inch roof

sheathing that the red coating quickly dis-

appeared from the Freud Diablo blades

we like to use. Since we never experienced

this when cutting AdvanTech subflooring

— another Huber OSB sheathing made

with the same resins but without the over-

lay — we assumed that the wear on the

blades was caused by the overlay. Most of

the roofs we frame have lots of hips and

valleys, and with the Zip System panels,

the many cuts required were not as clean

as we were used to.

We try to keep cutting to a minimum

when sheathing walls by running the pan-

els over door and window openings, then

coming back later with a router to cut out

the openings. On our first Zip house, our

carbide router bits lasted about half as

long as they last on houses with regular

OSB sheathing.

Taping the SeamsWe sheathe walls while they are on the

ground whenever possible, which means

that we usually tape the seams at the same

time. To keep the framing process mov-

ing along, we’ve learned to nail off the

seams first, then have one crew member

tape them while the rest of the crew fin-

ishes nailing off the rest of the panels.

Because the panels are stamped with stud

locations and nail spacing, we have fewer

missed nails. And when the time comes to

install siding, it’s easier to hit the framing.

Some building inspectors like to have

a look at the nailing before the house is

wrapped, which obviously complicates

matters a bit when using the Zip System.

Fortunately, the tape is thin enough that an

inspector can see or feel the nail spacing to

determine whether the fasteners are over-

driven. Some inspectors are a little stricter

and want to actually see the bare nails, in

Figure 1. Zip wall panels are premarked for 16-inch and 24-inch on-center stud layouts and have a self-spacing profile along their long edges (top and inset). The author uses a router to cut out door and window openings (above); he’s found that router bits tend to wear faster when cutting Zip panels than they do when cutting standard OSB sheathing, probably because of the denser material and resin-impregnated overlay.

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which case we can leave the tape off the

corners and a few seams, then apply the

tape after the walls are raised.

Tape sizes. Zip tape comes in 33⁄4-inch

and 6-inch widths and consists of a polyole-

fin film with an acrylic adhesive. It’s thinner

and less gummy than butyl- and asphalt-

based tapes and can be repositioned dur-

ing installation. According to Huber, the

tape can be applied to surfaces as cold as

20°F as long as they’re dry to the touch and

frost-free. The manufacturer warrants that

taped and installed Zip panels can be left

exposed to the weather and UV rays for up

to 120 days.

Application. The fastest way to apply

Zip system tape is with Huber’s stout new

tape gun, which resembles the dispensers

used to tape boxes together (Figure 2). The

gun’s built-in roller makes it easy to apply

enough pressure to activate the tape and

smooth out air bubbles or wrinkles. The

gun also has a spool that automatically

rolls up the release paper on the tape. It

takes a crew member only about 10 min-

utes to tape a 32-foot-by-16-foot wall.

Keeping the tape straight on runs more

than 5 feet long can be tricky, though. So

for longer seams, we tack the tape down

at one end, pull an 8- to 10-foot length off

the gun so that the tape is straight, and

then lay down the tape so that it’s centered

over the seam. If there are any splices,

we overlap the tape at the joint by a cou-

ple of inches. After taping, we use the Zip

System’s J-roller to smooth out any wrin-

kles and activate the tape.

Zip tape can also be applied manually.

After pulling lengths of tape off the roll

and cutting them to length, we pull off the

release paper as we’re taping the seam,

then go back over the seam with the J-roller.

This method takes a lot of time, so we use

it mainly for inside corners and other odd

configurations (Figure 3, facing page).

In rainy conditions, we keep the panels

covered by a tarp so they stay dry. That way,

we’re always sheathing with dry panels, re-

gardless of the previous night’s conditions.

Figure 2. The author’s crew uses the panel manufacturer’s guns to tape seams (left). The tape gun has a built-in roller, but the crew also uses a J-roller to make sure the tape is firmly applied (top and above).

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FEBRUARY 2011 l JLC l 6

If it’s raining while we’re sheathing, we

don’t tape the seams immediately; instead,

we return later and “blow-dry” the seams

with a backpack blower (Figure 4). One

person walks down the seam blowing off

the water, and another person follows

with the tape. If it’s impossible to keep the

sheathing dry enough, we wait until con-

ditions improve and the surface has dried

off before coming back to tape.

Windows and DoorsFor window and door installations, we use

the same basic flashing techniques with

Zip sheathing that we use for walls wrapped

with housewrap. The one big difference is

that we’re ultimately relying on the adhe-

sive bond between the tape and the

sheathing to keep water out of the wall.

First, we cover the rough sill with 6-inch

Zip tape or less-expensive 9-inch Vycor or

Moistop, lapping the flashing out and over

the sheathing (Figure 5, next page). At the

bottom corners of the opening, we use either

a flexible flashing tape or Vycorner prefabri-

cated self-adhering corners (866/333-3726,

graceconstruction.com). Then we caulk the

back of the unit’s nailing fins with a flexible

Figure 3. Corners are typ-ically taped by hand (far left and left), though the tape gun is sometimes used for outside corners (below left). A corner tool included in the gun kit is useful for applying pres-sure to inside corners and valleys (below).

Figure 4. Zip tape can’t be installed on wet surfaces, so a backpack leaf blower is used to dry off the seams in damp conditions.

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7 l JLC l FEBRUARY 2011

On Site With Zip System Sheathing

adhesive and set the window into the open-

ing. Next, we flash the fins to the sheathing,

making sure to firmly J-roll the flashing tape

to the wall and nail fins. Finally, we install

the head flashing over the trim at the top of

the window, taping the Z-metal to the wall

with Zip tape.

Huber’s 6-inch-wide Zip tape costs a lit-

tle more than the 9-inch-wide butyl- and

asphalt-based peel-and-stick flashing tapes

we typically use, but I think it’s a far bet-

ter product. We’ve left windows and doors

flashed with Zip tape for over a month

without a single corner or edge peeling

off the sheathing (a problem we’ve had

with many other peel-and-stick tapes).

Unfortunately, Zip tape is approved as a

flashing tape only with Zip sheathing and

might be red-tagged by your inspector on

regular OSB or plywood.

Roof PanelsNormally, we frame roofs 24 inches on-

center with 7⁄16-inch roof sheathing, so we

have to use H-clips. But the Zip roof panels

we use are true 1⁄2-inch OSB with a 32/16

span rating and they don’t require edge

support. This simplifies installation some-

what but presents a potential problem:

Figure 6. Zip roof panels provide good traction (left), thanks to grit added to the overlay during production. The author’s crew sets up toeboards for roof pitches steeper than 8/12 (above).

Figure 5. Either regular peel-and-stick flashing tape (left) or 6-inch-wide Zip tape can be used to flash doors and windows to the wall pan-els. Above, a worker seals a metal cap flashing with Zip tape.

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8 l JLC l FEBRUARY 2011

Since the long edges are self-spacing, the

spacer lips on the sheathing can some-

times overlap, lifting the edge of the uphill

sheet slightly. To avoid this problem, we

begin nailing along the bottom of the

sheathing at each rafter to pull the sheath-

ing tight to the framing before nailing off

the rest of the sheathing.

In dry weather, Zip roof panels provide

plenty of traction, thanks to the grit in the

overlay (Figure 6, previous page). The

panels are slicker in wet weather, but not

noticeably more so than regular OSB or

plywood sheathing. In most conditions,

we can comfortably frame up to about an

8/12 roof without using toeboards.

Taping. On roof pitches less than 8/12,

taping roof seams is a very quick process

(Figure 7). For example, it takes about

15 minutes to tape and J-roll a 20-foot-by-

30-foot section of 7/12 roof.

On roofs steep enough to require toe-

boards, however, I think that the benefits

of Zip sheathing are outweighed by the

extra labor required to tape the seams.

On a recent 12/12-pitch roof, for instance,

we needed more toeboards to get lever-

age on the tape gun and J-roller than we

needed to actually sheathe the roof. And,

of course, all of the nail holes from the toe-

boards have to be taped. In fact, it proba-

bly takes twice as much labor to sheathe

and tape a steep Zip System roof as it does

to sheathe the roof conventionally and roll

out underlayment. So in the future we’ll

stick to OSB sheathing for steep roofs.

Underlayment. Manufacturers and

local codes may require an additional

underlayment for shallow-pitched roofs,

depending on the roofing material. There

is a two-layer underlayment requirement

in most building codes for roof slopes

between 2/12 and 4/12, and a taped Zip

roof replaces the first layer only. Also, when

it comes time to strip off the old shingles

and reroof, new underlayment will be

required over the Zip sheathing regardless

of the roof pitch.

Eaves, valleys, hips, and ridges. The

wider 6-inch Zip tape is ideal for valleys,

though Huber says that overlapping the

33⁄4-inch-wide tape by at least 1 inch is

okay, too. In some areas, code may require

an additional self-adhering valley flashing.

Hips and ridges are also taped, and we tape

step flashings to sidewalls where necessary

(Figure 8, next page).

At the eaves, ice barrier membranes may

be required in certain climates. They’re

not required in our coastal climate, but

my roofer tells me that they would be if

we were building farther up in the moun-

tains. Huber allows any self-adhering ice

barrier with an ICC-ES report (or equiva-

lent) to be used over the Zip sheathing.

Cost In my area, Zip System sheathing tends

to cost about twice as much as compara-

ble OSB sheathing. Currently, we’re pay-

ing $7.67 per sheet for OSB sheathing and

$14.63 per sheet for Zip wall panels. Zip

roof panels are twice as expensive as both

AdvanTech and Edge Gold roof sheathing.

Figure 7. On shallow pitches, seams can be quickly taped as the roof is sheathed (top left). Roof penetrations (top right) and roof-to-wall intersections (above) are also sealed with tape — which is guaranteed to remain watertight for up to 120 days — before being covered.

On Site With Zip System Sheathing

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Posted with permission from the February 2011 issue of JLC - The Journal of Light Construction magazine. © Hanley Wood. #1-28508325 Managed by The YGS Group, 717.505.9701. For more information visit www.theYGSgroup.com/reprints.

After several houses, we’ve learned that

the installed cost for Zip wall sheathing —

including the labor to install the tape but

not the cost of the tape itself — is roughly

equal to the installed cost of OSB plus

Tyvek. The extra cost, then, is in the tape.

About one box of tape (a box contains

12 rolls, at 90 lineal feet per roll) is need-

ed to seal a unit (70 to 80 pieces) of 4x8 Zip

panels; for a typical 100-sheet house, that’s

16 rolls of tape. In addition, we use two or

three rolls of Zip tape for flashing windows

and doors and taping step flashing and Z-

metal to the wall. Tape costs around $28 per

roll, so using Zip panels adds about $500

to the cost of a 3,000-square-foot house.

We’re not convinced that Zip roof

sheathing is cost-effective (particularly

on steep roofs), since our roofing sub can

roll out underlayment and cover the roof

completely the same day he starts shin-

gling. If we were trying to build tighter

homes in an area that had a colder cli-

mate and a stricter energy code, though,

the added cost might make more eco-

nomic sense.

But with or without the energy savings,

we’re sold on Zip wall sheathing. We can

tape the walls while we’re framing and

rigging them to be lifted into place, so we

don’t lose any time; and we avoid the lad-

der work that would be needed to hang

housewrap. In fact, we eliminate about a

day in the construction cycle that would

typically be spent installing housewrap,

detailing it correctly, and then — later —

fixing rips in it caused by wind or by other

tradesmen stubbing pipes or wires out

through the walls.

Also, since we protect the seams with

tape as we frame, the panels don’t absorb

moisture. This saves both time and money,

since in our climate we might sometimes

spend as much as $1,000 to run kerosene

heaters and dehumidifiers to dry out an

OSB-sheathed house before insulation.

Tim Uhler is a builder in Port Orchard, Wash.

Figure 8. After the step flashing and roofing have been installed, the author tapes flashing to the sidewalls with 6-inch tape (above photos). When all the panel joints have been taped, the shell is weathertight and ready for roofing and siding (left).

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WHEN IT COMES TO ENERGY EFFICIENCY, THE WRITING IS ON THE WALL.By significantly reducing air leakage, ZIP System® wall sheathing contributes to greater comfort and energy efficiency in a home.

*Savings vary - see zipsystem.com/energyefficiency for details. **Flotkoetter, Brent. “ZIP System® wall sheathing and energy performance” November 2008.

© 2011 Huber Engineered Woods LLC. ZIP System, the accompanying ZIP System logo and design are trademarks of Huber Engineered Woods LLC. Huber is a registered trademark of J.M. Huber Corporation. Patents Pending. HUB11-03/11

A superior building envelope is here. By simply taping panel seams with ZIP System™ tape, ZIP System®

wall sheathing effectively seals the wall system, decreasing unwanted air leakage into and out of the home.

This helps protect the R-value of insulation**, reducing heating and cooling costs*. With a revolutionary

built-in weather resistant barrier, ZIP System wall sheathing is the only all-in-one solution that delivers the

strength, durability and efficiency of engineered wood while sealing out air and water. It’s not surpris-

ing builders everywhere are turning to ZIP System sheathing as an easier, tighter alternative to help

achieve new energy code requirements. Say hello to the future of energy-efficiency, and good-bye

to housewrap—once and for all.

For more information or to find a retailer, please visit www.zipsystem.com/energyefficiency

Limitations and restrictions apply - visit zipsystem.com for details.

Building site courtesy of Miller & Smith.

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